I knew that this would be the perfect story for Hollywood! He is producing it but he doesn’t have the rights to the book that is being written by the widow, Michael Mann jumped on that right away and outbid everyone:

Johnny Depp is planning a film about a former Russian security agent whose poisoning in London has touched off an international mystery, according to the trade magazine Variety one of three possible Hollywood projects about the case.
One of the other projects, involving the director Michael Mann, came after Columbia Pictures agreed to pay $1.5 million for the film rights to a book about the former Russian agent, Alexander Litvinenko, being co-written by his widow and a close friend, the report said.
Warner Bros., which was outbid for that book, acquired the rights to a book by Alan Cowell, a New York Times reporter, which is expected to be published next year by Doubleday, Variety said. Depp’s production company, Infinitum Nihil, will produce the film and the actor could star in it.
[…]
Litvinenko fled to Britain, was granted asylum and became a Kremlin critic in exile. The former FSB agent died in November, several weeks after falling ill with what was later determined to be poisoning by the rare radioactive isotope polonium-210.
Before his death, he said he fell ill after meeting in London with an Italian security expert to discuss possible suspects in the killing of the Russian journalist Anna Politkovskaya a month earlier. In her coverage of Chechnya, Politkovskaya was highly critical of alleged human rights violations by Russian forces and by Kremlin-backed Chechen officials.